Refactor asset type handling in AssetController schema

- Replaced native enum for asset types with a constant array using z.enum for improved type safety and maintainability in create and update asset schemas.

backend-api/src/controllers/AssetController.ts

@@ -3,17 +3,18 @@ import {z} from 'zod';
 import {AssetService} from '../services/AssetService';
 import {AssetRepository} from '../repositories/AssetRepository';
 import {getUserId} from '../middleware/auth';
-type AssetType = 'cash' | 'investment' | 'property' | 'vehicle' | 'other';
+
+const ASSET_TYPES = ['cash', 'investment', 'property', 'vehicle', 'other'] as const;
 
 const createAssetSchema = z.object({
   name: z.string().min(1),
-  type: z.nativeEnum(AssetType),
+  type: z.enum(ASSET_TYPES),
   value: z.number().min(0),
 });
 
 const updateAssetSchema = z.object({
   name: z.string().min(1).optional(),
-  type: z.nativeEnum(AssetType).optional(),
+  type: z.enum(ASSET_TYPES).optional(),
   value: z.number().min(0).optional(),
 });